Special Seminar

Speaker: Naritaka Oshita (RIKEN)
Title: Black hole ringing and thermal ringdown
Date (JST): Tue, Nov 08, 2022, 14:00 - 15:00
Place: Hybrid
Abstract: A gravitational wave from a binary black hole merger is an important probe to test gravity. Especially, the observation of ringdown may allow us to perform a robust test of gravity as it is a superposition of excited quasi-normal (QN) modes of a Kerr black hole. The excitation factor is an important quantity that quantifies the excitability of QN modes and is independent of the initial data of the black hole.
In this talk, I will show which QN modes can be important (i.e., have higher excitation factors) and will discuss how we can determine the start time of ringdown to maximally enhance the detectability of the QN modes.
Also, I will introduce my recent conjecture on the modeling of ringdown waveform: the thermal ringdown model in which the ringdown of rapidly spinning black holes can be modeled by the Fermi-Dirac distribution. As tentative evidence, I will show (i) the similarity between the distribution of Kerr QN modes and that of the Matsubara poles and (ii) the would-be Fermi degeneracy in the ringdown spectrum of a near-extremal black hole for which the Hawking frequency (or Hawking temperature) is close to zero.
Remarks: Lecture hall (in hybrid format)